It hasn't been too bad in any of my groups, because while the cleric isn't using his spells to heal, he is using his spells to cast other effects in combat. It doesn't seem to change the individual encounter so much as the long term viability of the cleric.
That having been said, both of the clerics in my campaigns (one 3rd level campaign, one 12th level campaign) have taken the selective channeling feat so that they can only affect their allies, and we haven't had too many encounters against the undead.
In fact, the biggest place where I could see this as an abuse is in combats with undead, because they are getting dual purpose out of that ability, damaging the enemies and healing their foes at the same time. As I have said though, most encounters with undead have been more or less minor encounters, so its hard to tell how critical this change will be.
When we started using this in the Alpha, I did have a cleric that more or less straight converted his character and took the ability to turn evil outsiders, before there was a selective channeling feat, and we had more important encounters with the undead, but then in that campaign (which ended at 7th level), the turnings came up front in the combat, and it couldn't be used in combat as effectively, and in that campaign, it seemed to work as well.
So I guess in the end I'm kind of interested in seeing a nice balanced adventuring day that features important undead encounters and non undead encounters now that the clerics can take selective channeling.
Other than vs. undead, the channels in my game have mostly been used out of combat. That has made combats a bit easier by almost always having everyone at full strength.
I think in the middle of combat a channel isn't really that much more healing than a cleric could do with a spell:
1st level: 3.5 to all vs. 5.5 to one
3rd level: 7 to all vs. 12 to one
5th level: 10.5 to all vs. 18.5 to one
10th level: 17.5 to all vs. 32.5 to one or 14.5 to all
After that heal changes the game a lot.
Other than vs. undead, the channels in my game have mostly been used out of combat. That has made combats a bit easier by almost always having everyone at full strength.
I think in the middle of combat a channel isn't really that much more healing than a cleric could do with a spell:
1st level: 3.5 to all vs. 5.5 to one
3rd level: 7 to all vs. 12 to one
5th level: 10.5 to all vs. 18.5 to one
10th level: 17.5 to all vs. 32.5 to one or 14.5 to allAfter that heal changes the game a lot.
I agree that the per encounter effect didn't really seem quite as dramatic, and in our Alpha games, before selective channeling, most of the healing seemed to take place just after the fight.
Also, even in my high level campaign with a cleric that could channel energy day and night, he whipped out a heal spell because the barbarian was getting trounced, so it doesn't obviate other spells.
In the undead fights, the dual purpose doesn't so much ruin encounters as much as its almost like having an extra character, because they don't have to choose between helping the party or attacking the undead, although I will also add the following caveat . . . the encounter doesn't change a whole lot if PCs don't go in injured.
In other words, if the cleric is trying to down the undead quickly, and the PCs aren't injured, even this "issue" isn't much of one. Its more of a change later in the fight.
Then again, my campaign was already using the Complete Divine alternative rule that did 1d6/level per turn against undead, so as far as offensive capability, this went down a bit.